Refrigeration apparatus with defrost means



Nov. 23, 1965 L. M. BLAIN ETAL REFRIGERATION APPARATUS WITH DEFROST MEANS Filed Feb. 21, 1963 I CONDENSER u loo lOl Fig.5

INVENTORS. LELAND M. BLAIN BY SHERJANC? S. SIDHU AT TYs.

United States Patent 3,218,823 REFRIGERATION APPARATUS WITH DEFROST MEANS Leland M. Blain, Sandcreek, and Sherjang S. Sidhu,

Jackson, Mich., assignors to Revco, Inc., Deerfield,

Mich., a corporation of Michigan Filed Feb. 21, 1963, Ser. No. 274,883 3 Claims. (Cl. 62-278) This invention relates generally to refrigeration apparatus and in particular to refrigeration apparatus wherein a bypass around a refrigerant expansion means is utilized.

In recent years the use of parallel circuits in refrigeration systems has increased tremendously, particularly in the area of applying a hot gas defrost through an auxiliary circuit and coil to remove ice and frost from an evaporator coil. The auxiliary coil is connected in parallel with at least the refrigerant expansion means, whether it be a capillary line or a valve type refrigerant expander, and ordinarily a valve is employed in the auxiliary circuit to control the fiow of hot gas refrigerant from the high pressure side of the compressor to the auxiliary coil. While this invention is particularly adaptable for use with the hot gas, auxiliary coil defrost system to be described herein it is useful for any refrigeration application wherein an expansion means is to be bypassed.

The dimculties encountered in bypassing a refrigerant expansion means with an auxiliary circuit arise when the valve means or other flow control means controlling the flow of hot gas refrigerant into the auxiliary circuit is disposed only in the auxiliary circuit itself. When the valve is opened to allow hot gas flow through the auxiliary circuit, most of the refrigerant does flow through the auxiliary circuit. But, since there has been no corresponding closure of the circuit that has been bypassed, there still is some flow through the refrigeration expansion means since the two circuits are now operating in parallel. This continued flow, even during the hot gas defrost is most undesirable since it continues to form frost or cause icing on the portion of the evaporator immediately following the refrigerant expansion means. That is, the first coils of the evaporator continue to ice causing an excessive amount of ice formation since this part of the evaporator can never be defrosted. Further, the icing on this portion of the coil slows the defrost period of the remainder of the evaporator coil because of the cooling of the ambient atmosphere and the conduction of cold from the ice to the remainder of the coil.

It is, accordingly, an object of this invention to provide an improved refrigeration apparatus in which flow through one of two parallel circuits may be halted without use of a valve or other mechanical closure.

It is a further object of this invention to provide an improved refrigeration system in which undesirable icing effects are avoided on an evaporator means when a refrigerant expansion means is operating in parallel circuit realtionship with an auxiliary circuit.

In accordance with the above objects there is disclosed and described herein refrigeration apparatus comprising a first circuit including refrigerant circulating means connected to and adapted to circulate refrigerant through a refrigerant expansion means, and a second circuit including means for controlling refrigerant flow in said second circuit wherein said second circuit is connected to the first circuit to bypass the refrigerant expansion means. The connection of the second circuit to the first circuit upstream of the refrigeration expansion means comprises a first conduit having a substantially straight portion wherein one end of said conduit is a part of the first circuit and the other end is a part of the second circuit. A wall of the substantially straight portion of the first conduit has an aperture formed therein. A second conduit connected to the substantially straight portion of the first conduit and communicating with the inside of the first conduit through the aperture formed in the wall of the first conduit conducts refrigerant to the refrigerant expansion means when there is no refrigerant flow in the second circuit.

The invention also may be described as refrigeration apparatus comprising a first circuit including a refrigerant circulating means connected to and adapted to circulate refrigerant through a refrigerant expansion means, a second circuit connected to bypass said refrigerant expansion means in said first circuit, and means for diverting refrigerant flow to said second circuit. A T-shaped connector connects the second circuit and the first circuit before the refrigerant expansion means in the first circuit, One arm and one leg of the T-shaped connector are in the first circuit, the leg carrying refrigerant to the refrigerant expansion means. The other arm of the T-shaped connector carries refrigerant to the second circuit.

Other objects, features, and advantages will become apparent when the following description is taken in conjunction with the accompanying drawing in which:

FIG. 1 is a circuit diagram of refrigeration apparatus embodying the teachings of this invention;

FIG. 2 is a circuit diagram illustrating a modification embodying the teachings of this invention; and

FIG. 3 is a circuit diagram of an additional modification embodying the teachings of this invention.

Referring to FIG. 1 there is shown a refrigeration circuit illustrating the operation of the invention, it being kept in mind that this invention may be utilized in other types of refrigeration systems.

A compressor 10 is connected through a conduit 11 to a condenser 20. The condenser 20 is connected through a conduit 21 to a drier means 30 and a valve 70 where the circuit divides into parallel operation. The connection at the parallel circuit division may be described as a T-shaped connector designated generally at 100 having a leg 101 and arms 102 and 103. The arm 102 and the leg 101 comprise a portion of the first circuit, While the arm 103 comprises the start of the second circuit.

The connection may also be described as a first conduit (102, 103) having a substantially straight portion wherein one end I02 of said conduit is a part of said first circuit and the other end 103 is a part of the second cir cuit. A wall of the substantially straight portion of the firs-t conduit has an aperture 104 formed therein. A second conduit 101 is connected to the substantially straight portion of the first conduit and communicates with the inside of the first conduit through the aperture 104 formed in the wall of the first conduit. The second conduit 101 conducts refrigerant to the refrigerant expansion means 40 when there is no refrigerant flow in the second circuit.

Continuing with the description of the circuit, the first circuit includes the drier means 30, a refrigerant expansion means 40 (shown herein as a capillary line although it may be a valve type expansion means), an evaporator means 50 and a suction line 60 completing the circuit back to the compressor 10.

The second circuit comprises the solenoid controlled valve 70 (which may be controlled in any manner shown in the prior art which effects the desired operation), an auxiliary defrost means disposed in heatexchange relationship with the evaporator means 50, and a second or auxiliary refrigeration expansion means conducting the hot gas refrigerant back to the suction line 60 and/or the compressor 10.

In operation, the compressor 10 discharges refrigerant under high pressure through the conduit 11 to the condenser means 20 and through the conduit 21 to the drier 30, the valve 70 being closed during the normal refrigeration cycle. The compressed refrigerant is expanded through the expansion means 40 into the evaporator means 50 affecting a cooling of the area surrounding the evaporator means 50. The spent refrigerant is returned through the suction line 60 to the compressor to be recompressed and utilized again.

When the evaporator means has gained a coating of ice and frost the valve 70 may be opened to initiate a defrost cycle and to conduct the hot gas directly to the auxiliary defrost coil 80 disposed in heat-exchange relationship with the evaporator means 50. The passage of the hot gas and/or liquified refrigerant through coil 80 warms the evaporator means 50 thereby melting the frost and ice therefrom. The hot gas and/or liquified refrigerant is returned from the auxiliary defrost coil 10 through the second expansion means 90 to the compressor 10.

The difiiculties arise in this and other circuits when the valve 70 is opened and there is still a refrigerant flow through the first expansion means 40 to the evaporator means 50 causing either the retention of frost and ice on the first few coils of the evaporator means 50 or the formation of more frost and ice on said coils. This is true since the two circuits are operating in parallel and, although the major flow is through the valve 70, there is still flow through the expansion means 40 because the first circuit remains open at all times. Various solutions have been proposed to prevent this buildup. For example, the capillary means 40 has been wrapped around the defrost inlet tube but this does not assist in eliminating the ice buildup on the evaporator means 40. An eight watt heater has been wrapped around the drier and turned on during defrost but the rise in temperature was not sufiicient to stop the flow through the capillary means 40 during defrost. An increased wattage heater (33 Watts) was successfully used and sufficient to raise the condenser outlet temperature high enough to stop the flow through the capillary tube and cause the ice to disappear from the evaporator means. However, the added expense in operation and in original cost is much too great for use from an economic standpoint. In addition, a heat exchange between the capillary means 40 and the compressor discharge and/or the defrost inlet has been proposed, but this does not effectively control the ice buildup on the evaporator means 50 during the defrost cycle.

Utilizing the configuration shown in FIG. 1, the ice buildup and retention on the evaporator means 50 was halted during the defrost cycle. It is believed that the flow of the hot gas refrigerant through the straight or arm portion 102, 103 of the T-shaped connector into the auxiliary circuit acts to reduce the pressure in the leg 101 to prevent any pressure feed through the expansion means 40, or, to at least reduce the pressure at the mouth of the expansion means 40 below that necessary to force refrigerant through the expansion means 40 and to expand it to cause an ice buildup on the first portion of the evaporator means 50. In the preferred embodiment the optimum size of conduits producing best results were inch for the arms 102,103 and the leg 101. The most efficient operation is obtained when the position of the leg portion of the T-shaped connector is pointed upwardly and maintained within a variance of 45 from the vertical. It is obvious that various size conduits may be utilized to producethe reduction of pressure in the drier 30 and/or at the mouth of the expansion means 40 to prevent ice buildup, if the sizes are such in conjunction with the systems other constants to produce the suction or decrease of pressure desired without regard to the geometric configuration or displacement of the T-shaped connection 100.

Referring to FIG. 2 there is shown a modification in which the drier 30 is placed in the conduit 21 leading from A the condenser before the T-shaped connection 100. In FIG. 3 the T-shaped connection is taken off from the high pressure discharge side of the compressor 10 through the conduit 11 before the condenser 20 and drier 30, the condenser and drier then connected directly to the expansion means 40.

In conclusion it is to be noted that the embodiments disclosed and described herein are meant to be illustrative only and not limiting in any sense. The embodiments serve to illustrate the spirit and scope of the invention.

We claim as our invention:

1. Refrigeration apparatus comprising a first circuit including refrigerant circulating means connected to and adapted to circulate refrigerant through a condenser means, a refrigerant expansion means, and an evaporator means; and a second circuit including means for controlling refrigerant flow in said second circuit and auxiliary coil means disposed in heat exchange relationship with said evaporator means of said first circuit; said second circuit being connected to said first circuit to bypass said refrigerant expansion means and return refrigerant to said refrigerant circulating means; a connection of said second circuit to said first circuit upstream of said refrigerant expansion means and downstream of said condenser means comprising a first conduit having a substantially straight portion wherein one end of said conduit is a part of said first circuit and the other end of said conduit is a part of said second circuit, a wall of said substantially straight portion of said first conduit having an aperture formed therein, and a second conduit substantially perpendicular to and connected to said substantially straight portion of said first conduit and communicating with the inside of said first conduit through said aperture formed in the wall of said first conduit; said second conduit conducting refrigerant to said expansion means when there is no refrigerant flow in said second circuit; refrigerant flow in said second circuit being operative to reduce pressure at an inlet of said expansion means below that necessary for appreciable refrigeration thus allowing the entire evaporator means to be defrosted.

2. Refrigeration apparatus comprising a first circuit including refrigerant circulating means connected to and adapted to circulate refrigerant through a condenser means, a drier means, a refrigerant expansion means, and an evaporator means; and a second circuit including means for controlling refrigerant fiow in said second circuit and auxiliary coil means disposed in heat exchange relationship with said evaporator means of said first circuit; said second circuit being connected to said first circuit to bypass said refrigerant expansion means and return refrigerant to said refrigerant circulating means; a connection of said second circuit to said first circuit upstream of said refrigerant expansion means and downstream of said drier means comprising a first conduit having a substantially straight portion wherein one end of said conduit is a part of said first circuit and the other end of said conduit is a part of said second circuit, a wall of said substantially straight portion of said first conduit having an aperture formed therein, and a second conduit substantially perpendicular to and connected to said substantially straight portion of said first conduit and communicating with the inside of said first conduit through said aperture formed in the wall of said first conduit; said second conduit conducting refrigerant to said expansion means when there is no refrigerant flow in said second circuit; refrigerant flow in said second circuit being operative to reduce pressure at an inlet of said expansion means below that necessary for appreciable refrigeration thus allowing the entire evaporator means to be defrosted.

3. Refrigeration apparatus comprising a first circuit including refrigerant circulating means connected to and adapted to circulate refrigerant through a condenser means, a drier means, a refrigerant expansion means, and an evaporator means; and a second circuit including means for controlling refrigerant flow in said second circuit and auxiliary coil means disposed in heat exchange relationship with said evaporator means of said first circuit; said second circuit being connected to said first circuit to bypass said refrigerant expansion means and return refrigerant to said refrigerant circulating means; a connection of said second circuit to said first circuit upstream of said drier means and downstream of said condenser means comprising a first conduit having a substantially straight portion wherein one end of said conduit is a part of said first circuit and the other end of said conduit is a part of said second circuit, a wall of said substantially straight portion of said first conduit having an aperture formed therein, and a second conduit substantially perpendicular to and connected to said substantially straight portion of said first conduit and communicating with the inside of said first conduit through said aperture formed in the Wall of said first conduit; said second conduit conducting refrgierant to said expan- 6 sion means when there is no refrigerant flow in said second circuit; refrigerant flow in said second circuit being operative to reduce pressure at an inlet of said expansion means below that necessary for appreciable refrigeration 5 thus allowing the entire evaporator means to be defrosted.

References Cited by the Examiner UNITED STATES PATENTS ROBERT A. OLEARY, Primary Examiner.

MEYER PERLIN, Examiner. 

1. REFRIGERATION APPARATUS COMPRISING A FIRST CIRCUIT INCLUDING REFRIGERANT CIRCULATING MEANS CONNECTED TO AND ADAPTED TO CIRCULATE REFRIGERANT THROUGH A CONDENSER MEANS, A REFRIGERANT EXPANSION MEANS, AND AN EVAPORATOR MEANS; AND A SECOND CIRCUIT INCLUDING MEANS FOR CONTROLLING REFRIGERANT FLOW IN SAID SECOND CIRCUIT AND AUXILIARY COIL MEANS DISPOSED IN HEAT EXCHANGE RELATIONSHIP WITH SAID EVAPORATOR MEANS OF SAID FIRST CIRCUIT; SAID SECOND CIRCUIT BEING CONNECTED TO SAID FIRST CIRCUIT TO BYPASS SAID REFRIGERANT EXPANSION MEANS AND RETURN REFRIGERANT TO SAID REFRIGERANT CIRCULATING MEANS; A CONNECTION OF SAID SECOND CIRCUIT TO SAID FIRST CIRCUIT UPSTREAM OF SIAD REFRIGERANT EXPANSION MEANS AND DOWNSTREAM OF SAID CONDENSER MEANS COMPRISING A FIRST CONDUIT HAVING A SUBSTANTIALLY STRAIGHT PORTION WHEREIN ONE END OF SAID CONDUIT IS A PART OF SAID FIRST CIRCUIT AND THE OTHER END OF SAID CONDUIT IS A PART OF SAID SECOND CIRCUIT, A WALL OF SAID SUBSTANTIALLY STRAIGHT PORTION OF SAID FIRST CONDUIT HAVING AN APERTURE FORMED THEREIN, AND A SECOND CONDUIT SUBSTANTIALLY PERPENDICULAR TO AND CONNECTED TO SAID SUBSTANTIALLY STRAIGHT PORTION OF SAID FIRST CONDUIT AND COMMUNICATING WITH THE INSIDE OF SAID FIRST CONDUIT THROUGH SAID APERTURE FORMED IN THE WALL OF SAID FIRST CONDUIT; SAID SECOND CONDUIT CONDUCTING REFRIGERANT TO SAID EXPANSION MEANS WHEN THERE IS NO REFRIGERANT TO SAID EXPANSION MEANS WHEN THERE FLOW IN SAID SECOND CIRCUIT BEING OPERATIVE TO REDUCE PRESSURE AT AN INLET OF SAID EXPANSION MEANS BELOW THAT NECESSARY FOR APPRECIABLE REFRIGERATION THUS ALLOWING THE ENTIRE EVAPORATOR MEANS TO BE DEFROSTED. 